Welcome to the Slackware Documentation Project

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
slackbook:bash [2012/09/08 18:00 (UTC)]
mfillpot [Tab Completion] updated section to match original with formatting
slackbook:bash [2012/10/14 15:52 (UTC)] (current)
mfillpot removed all bash flags
Line 162: Line 162:
 dealing with long filenames: tab completion. ​ Tab completion enables dealing with long filenames: tab completion. ​ Tab completion enables
 you to type just enough of the filename to uniquely identify it, then you to type just enough of the filename to uniquely identify it, then
-by hitting the <​key>​TAB</​key>​ key, **//​bash//​** will fill in+by hitting the <key>'TAB'</​key>​ key, **//​bash//​** will fill in
 the rest for you.  Even if you haven'​t typed in enough text to uniquely the rest for you.  Even if you haven'​t typed in enough text to uniquely
 identify a filename, the shell will fill in as much as it can for you. identify a filename, the shell will fill in as much as it can for you.
Line 169: Line 169:
 ===== Input and Output Redirection ===== ===== Input and Output Redirection =====
  
-One of the defining features of Linux and other UNIX-like operating systems is the number of small, relatively simple applications and the ability to stack them together to create complex systems. This is achieved by redirecting the output of one program to another, or by drawing input from a file or second program.+One of the defining features of Linux and other UNIX-like operating 
 +systems is the number of small, relatively simple applications and the 
 +ability to stack them together to create complex systems. ​ This is 
 +achieved by redirecting the output of one program to another, or by 
 +drawing input from a file or second program. 
 + 
 + 
 +To get started, we're going to show you how to redirect the output of a 
 +program to a file.  This is easily done with the '>'​ character. ​ When 
 +**//​bash//​** sees the '>'​ character, it redirects 
 +all of the standard output (also known as stdout) to whatever file name 
 +follows. 
  
-To get started, we're going to show you how to redirect the output of a program to a file. This is easily done with the '>'​ character. When bash sees the '>'​ character, it redirects all of the standard output (also known as stdout) to whatever file name follows. 
 <​code>​ <​code>​
 darkstar:~$ echo foo darkstar:~$ echo foo
Line 180: Line 191:
 </​code>​ </​code>​
  
-In this example, we show you what echo would do if its stdout was not redirected to a file, then we re-direct it to the /tmp/bar file. If /tmp/bar does not exist, it is created and the output from echo is placed within it. If /tmp/bar did exist, then its contents are over-written. This might not be the best idea if you want to keep those contents in place. Thankfully, bash supports '>>'​ which will append the output to the file.+ 
 +In this example, we show you what **//echo//** would 
 +do if its stdout was not redirected to a file, then we re-direct it to 
 +the ''​/tmp/bar'' ​file.  If ''​/tmp/bar''​ 
 +does not exist, it is created and the output from 
 +**//echo//** is placed within it.  If 
 +''​/tmp/bar'' ​did exist, then its contents are 
 +over-written. ​ This might not be the best idea if you want to keep 
 +those contents in place. ​ Thankfully, ​**//bash//** 
 +supports '>>'​ which will append the output to the file. 
  
 <​code>​ <​code>​
Line 194: Line 215:
 </​code>​ </​code>​
  
-You can also re-direct the standard error (or stderr) to a file. This is slightly different in that you must use '​2>'​ instead of just '>'​. (Since bash can re-direct input, stdout, and stderr, each must be uniquely identifiable. 0 is input, 1 is stdout, and 2 is stderr. Unless one of these is specified, bash will make its best guess as to what you actually meant, and assumed anytime you use '>'​ you only want to redirect stdout. 1> would have worked just as well.)+ 
 +You can also re-direct the standard error (or stderr) to a file.  This 
 +is slightly different in that you must use '​2>'​ instead of just '>'​. 
 +(Since ​**//bash//** can re-direct input, stdout, and 
 +stderr, each must be uniquely identifiable. ​ 0 is input, 1 is stdout, 
 +and 2 is stderr. ​ Unless one of these is specified, 
 +**//bash//** will make its best guess as to what you 
 +actually meant, and assumed anytime you use '>'​ you only want to 
 +redirect stdout. ​ 1> would have worked just as well.) 
  
 <​code>​ <​code>​
Line 204: Line 234:
 </​code>​ </​code>​
  
-You may also redirect the standard input (known as stdin) with the '<'​ character, though it's not used very often.+ 
 +You may also redirect the standard input (known as stdin) with the 
 +'<'​ 
 +character, though it's not used very often. 
  
 <​code>​ <​code>​
Line 210: Line 244:
 </​code>​ </​code>​
  
-Finally, you can actually redirect the output of one program as input to another. This is perhaps the most useful feature of bash and other shells, and is accomplished using the '​|'​ character. (This character is referred to as '​pipe'​. If you here some one talk of piping one program to another, this is exactly what they mean.)+ 
 +Finally, you can actually redirect the output of one program as input 
 +to another. ​ This is perhaps the most useful feature of 
 +**//bash//** and other shells, and is accomplished 
 +using the '​|'​ character. ​ (This character is referred to as '​pipe'​. 
 +If you here some one talk of piping one program to another, this is 
 +exactly what they mean.) 
  
 <​code>​ <​code>​
Line 220: Line 261:
 root      3202  0.0  0.0   ​1660 ​  536 tty6     ​Ss+ ​ Feb15   0:00 /​sbin/​agetty 38400 tty6 linux root      3202  0.0  0.0   ​1660 ​  536 tty6     ​Ss+ ​ Feb15   0:00 /​sbin/​agetty 38400 tty6 linux
 </​code>​ </​code>​
- 
 ===== Task Management ===== ===== Task Management =====
  
-bash has yet another cool feature to offer, the ability to suspend and resume tasks. This allows you to temporarily halt a running process, perform some other task, then resume it or optionally make it run in the background. Upon pressing CTRL-Z, bash will suspend the running process and return you to a prompt. You can return to that process later. Additionally,​ you can suspend multiple processes in this way indefinitely. The jobs built-in command will display a list of suspended tasks.+**//bash//** has yet another cool feature to offer, 
 +the ability to suspend and resume tasks. ​ This allows you to 
 +temporarily halt a running process, perform some other task, then 
 +resume it or optionally make it run in the background. Upon pressing 
 +<​key>'​CTRL'</​key>​+<​key>'​z'</​key>​**//bash//** will suspend 
 +the running process and return you to a prompt. You can return to that 
 +process later. ​ Additionally,​ you can suspend multiple processes in 
 +this way indefinitely. ​ The **//jobs//** built-in 
 +command will display a list of suspended tasks. 
  
 <​code>​ <​code>​
Line 231: Line 280:
 </​code>​ </​code>​
  
-In order to return to a suspended task, run the fg built-in to bring the the most recently suspended task back into the foreground. If you have mutiple suspended tasks, you can specify a number as well to bring one of them to the foreground.+ 
 +In order to return to a suspended task, run the 
 +**//fg//** built-in to bring the the most recently 
 +suspended task back into the foreground. If you have mutiple suspended ​ 
 +tasks, you can specify a number as well to bring one of them to the 
 +foreground. 
  
 <​code>​ <​code>​
Line 238: Line 293:
 </​code>​ </​code>​
  
-You can also background a task with (surprize) bg. This will allow the process to continue running without maintaining control of your shell. You can bring it back to the foreground with fg in the same way as suspended tasks.+ 
 +You can also background a task with (surprize) 
 +**//bg//**. This will allow the process to continue 
 +running without maintaining control of your shell. You can bring it 
 +back to the foreground with **//fg//** in the same 
 +way as suspended tasks.
  
 ===== Terminals ===== ===== Terminals =====
  
-Slackware Linux and other UNIX-like operating systems allow users to interact with them in many ways, but the most common, and arguably the most useful, is the terminal. In the old days, terminals were keyboards and monitors (sometimes even mice) wired into a mainframe or server via serial connections. Today however, most terminals are virtual; that is, they exist only in software. Virtual terminals allow users to connect to the computer without requiring expensive and often incompatible hardware. Rather, a user needs only to run the software and they are presented with a (usually) highly customizable virtual terminal.+Slackware Linux and other UNIX-like operating systems allow users to 
 +interact with them in many ways, but the most common, and arguably the 
 +most useful, is the terminal. In the old days, terminals were keyboards 
 +and monitors (sometimes even mice) wired into a mainframe or server via 
 +serial connections. Today however, most terminals are virtual; that is, 
 +they exist only in software. ​ Virtual terminals allow users to connect 
 +to the computer without requiring expensive and often incompatible 
 +hardware. Rather, a user needs only to run the software and they are 
 +presented with a (usually) highly customizable virtual terminal.
  
-The most common virtual terminals (in that every Slackware Linux machine is going to have at least one) are the gettys. agetty(8) runs six instances by default on Slackware, and allows local users (those who can physically sit down in front of the computer and type at the keyboard) to login and run applications. Each of these gettys is available on different tty devices that are accessible seperately by pressing the **ALT** key and one of the function keys from **F1** through **F6**. Using these gettys allows you to login multiple times, perhaps as different users, and run applications in those users' shells silmutaneously. This is most commonly done with servers which do not have X installed, but can be done on any machine. 
  
-On desktops, laptops, and other workstations where the user prefers a graphical interface provided by X, most terminals are graphical. Slackware ​includes many different graphical terminalsbut the most commonly used are KDE's konsole ​and XFCE's Terminal(1) as well as the old standby, xterm(1)If you are using a graphical interfacecheck your tool bars or menus. Each desktop environment or window manager has a virtual terminal (often called a terminal emulater), and they are all labelled differently. Typically though, you will find them under a "​System"​ sub-menu ​in desktop environmentsExecuting ​any of these will give you a graphical terminal and automatically run your default shell.+The most common virtual ​terminals ​(in that every Slackware Linux machine 
 +is going to have at least one) are the gettys. 
 +**//​agetty//​**(8) runs six instances by default on 
 +Slackware, ​and allows local users (those who can physically sit down in 
 +front of the computer and type at the keyboard) to login and run 
 +applications. Each of these gettys is available on different tty 
 +devices that are accessible seperately by pressing the 
 +<key>'ALT'</​key>​ key and one of the function keys from 
 +<​key>'​F1'</​key>​ through <​key>'​F6'</​key>​Using these gettys 
 +allows ​you to login multiple timesperhaps as different users, and run 
 +applications ​in those users' shells silmutaneouslyThis is most 
 +commonly done with servers which do not have 
 +**//X//** installed, but can be done on any machine.
  
 +
 +On desktops, laptops, and other workstations where the user prefers a
 +graphical interface provided by **//X//**, most
 +terminals are graphical. ​ Slackware includes many different graphical
 +terminals, but the most commonly used are KDE's
 +**//​konsole//​** and XFCE's
 +**//​Terminal//​**(1) as well as the old standby,
 +xterm(1). If you are using a graphical interface, check your tool bars
 +or menus. Each desktop environment or window manager has a virtual
 +terminal (often called a terminal emulater), and they are all labelled
 +differently. Typically though, you will find them under a //"​System"//​
 +sub-menu in desktop environments. Executing any of these will give you
 +a graphical terminal and automatically run your default shell.
 ===== Customization ===== ===== Customization =====
  
-By now you should be pretty familiar with bash and you may have even noticed some odd behavior. For example, when you login at the console, you're presented with a prompt that looks a bit like this.+By now you should be pretty familiar with 
 +**//bash//** and you may have even noticed some odd 
 +behavior. For example, when you login at the console, you're presented 
 +with a prompt that looks a bit like this. 
  
 <​code>​ <​code>​
-alan@darkstar:​~$ ​ +alan@darkstar:​~$ </​code>​ 
-</​code>​+ 
 However, sometimes you'll see a much less helpful prompt like this one. However, sometimes you'll see a much less helpful prompt like this one.
 +
  
 <​code>​ <​code>​
-bash-3.1$ ​ +bash-3.1$ </​code>​ 
-</​code>​+ 
 + 
 +The cause here is a special environment variable that controls the 
 +**//​bash//​** prompt. Some shells are considered 
 +//"​login"//​ shells and others are //"​interactive"//​ shells, and both types read 
 +different configuration files when started. Login shells read 
 +''/​etc/​profile''​ and 
 +''​~/​.bash_profile''​ when executed. Interactive shells 
 +read ''​~/​.bashrc''​ instead. This has some advantages 
 +for power users, but is a common annoyance for many new users who want 
 +the same environment anytime they execute 
 +**//​bash//​** and don't care about the difference 
 +between login and interactive shells. If this applies to you, simply 
 +edit your own ~/.bashrc file and include the following lines. 
 +(For more information on 
 +the different configuration files used, read the INVOCATION section of 
 +the **//​bash//​** man page.)
  
-The cause here is a special environment variable that controls the bash prompt. Some shells are considered "​login"​ shells and others are "​interactive"​ shells, and both types read different configuration files when started. Login shells read /​etc/​profile and ~/​.bash_profile when executed. Interactive shells read ~/.bashrc instead. This has some advantages for power users, but is a common annoyance for many new users who want the same environment anytime they execute bash and don't care about the difference between login and interactive shells. If this applies to you, simply edit your own ~/.bashrc file and include the following lines. (For more information on the different configuration files used, read the INVOCATION section of the bash man page.) 
  
 <​code>​ <​code>​
 +
 # ~/.bashrc # ~/.bashrc
 . /​etc/​profile . /​etc/​profile
Line 269: Line 383:
 </​code>​ </​code>​
  
-When using the above, all your login and interactive shells will have the same environment settings and behave identically. Now, anytime we wish to customize a shell setting, we only have to edit ~/​.bash_profile for user-specific changes and /​etc/​profile for global settings. Let's start by configuring the prompt. 
  
-bash prompts come in all shapes, colors, and sizes, and every user has their own preferances. Personally, I prefer short and simple prompts that take up a minimum of space, but I've seen and used mutli-line prompts many times. One personal friend of mine even included ASCII-art in his bash prompt. To change your prompt you need only to change your PS1 variable. By default, Slackware attempts to configure your PS1 variable thusly:+When using the above, all your login and interactive shells will have 
 +the same environment settings and behave identically. Now, anytime we 
 +wish to customize a shell setting, we only have to edit 
 +''​~/​.bash_profile''​ for user-specific changes and 
 +''/​etc/​profile''​ for global settings. Let's start by 
 +configuring the prompt. 
 + 
 + 
 +**//bash//** prompts come in all shapes, colors, and 
 +sizes, and every user has their own preferances. Personally, I prefer 
 +short and simple prompts that take up a minimum of space, but I've seen 
 +and used mutli-line prompts many times. One personal friend of mine 
 +even included ASCII-art in his bash prompt. To change your prompt you 
 +need only to change your PS1 variable. By default, Slackware attempts 
 +to configure your PS1 variable thusly: 
  
 <​code>​ <​code>​
 darkstar:~$ echo $PS1 darkstar:~$ echo $PS1
-\u@\h:​\w\$ ​ +\u@\h:\w\$ </​code>​
-</​code>​+
  
-Yes, this tiny piece of funny-looking figures controls your bash prompt. Basicaly, every character in the PS1 variable is included in the prompt, unless it is a escaped by a \, which tells bash to interpret it. There are many different escape sequences and we can't discuss them all, but I'll explain these. The first "​\u"​ translates to the username of the current user. "​\h"​ is the hostname of the machine the terminal is attached to. "​\w"​ is the current working directory, and "​\$"​ displays either a # or a $ sign, depending on whether or not the current user is root. A complete listing of all prompt escape sequences is listed in the bash man page under the PROMPTING section. 
  
-Since we've gone through all this trouble to discuss the default prompt, I thought I'd take some time to show you a couple example prompts and the PS1 variable values needed to use them.+Yes, this tiny piece of funny-looking figures controls your 
 +**//​bash//​** prompt. Basicaly, every character in 
 +the PS1 variable is included in the prompt, unless it is a escaped by a 
 +<​key>'​\'</​key>,​ which tells **//​bash//​** to 
 +interpret it. There are many different escape sequences and we can'​t 
 +discuss them all, but I'll explain these. ​ The first //"​\u"//​ translates to 
 +the username of the current user.  //"​\h"//​ is the hostname of the machine 
 +the terminal is attached to. //"​\w"//​ is the current working directory, and 
 +//"​\$"//​ displays either a <​key>'#'</​key>​ or a <​key>'​$'</​key>​ sign, 
 +depending on whether or not the current user is root.  A complete 
 +listing of all prompt escape sequences is listed in the 
 +**//​bash//​** man page under the PROMPTING section. 
 + 
 + 
 +Since we've gone through all this trouble to discuss the default 
 +prompt, I thought I'd take some time to show you a couple example 
 +prompts and the PS1 variable values needed to use them. 
  
 <​code>​ <​code>​
Line 291: Line 434:
 </​code>​ </​code>​
  
-For even more information on configuring your bash prompt, including information on setting up colored prompts, refer to /​usr/​doc/​Linux-HOWTOs/​Bash-Prompt-HOWTO. After reading that for a short while, you'll get an idea of just how powerful your bash prompts can be. I once even had a prompt that gave me up to date weather information such as temperature and barometric pressure! 
  
 +For even more information on configuring your bash prompt, including
 +information on setting up colored prompts, refer to
 +''/​usr/​doc/​Linux-HOWTOs/​Bash-Prompt-HOWTO''​. After
 +reading that for a short while, you'll get an idea of just how powerful
 +your **//​bash//​** prompts can be. I once even had a
 +prompt that gave me up to date weather information such as temperature
 +and barometric pressure!
 +
 +====== Chapter Navigation ======
 +
 +**Previous Chapter: [[slackbook:​shell|Basic Shell Commands]]**
 +
 +**Next Chapter: [[slackbook:​process_control|Process Control]]**
 ====== Sources ====== ====== Sources ======
 <!-- If you copy information from another source, then specify that source --> <!-- If you copy information from another source, then specify that source -->
- * Original source: [[http://​www.slackbook.org/​beta/#ch_bash]] +  ​* Original source: [[http://​www.slackbook.org/​beta]] ​\\
 <!-- Authors are allowed to give credit to themselves! --> <!-- Authors are allowed to give credit to themselves! -->
-<​!-- ​* Originally written by [[wiki:​user:​xxx | User X]] -->+  ​* Originally written by Alan Hicks, Chris Lumens, David Cantrell, Logan Johnson
 <!-- * Contrbutions by [[wiki:​user:​yyy | User Y]] --> <!-- * Contrbutions by [[wiki:​user:​yyy | User Y]] -->
  

In Other Languages
QR Code
QR Code slackbook:bash (generated for current page)